1. Field of Invention
The field of the present invention relates in general to digital filters and specifically finite impulse response filters.
2. Description of the Related Art
A finite impulse response (FIR) filter is a type of digital filter capable of affecting a response to an impulse which ultimately settles to zero. This type of filter can affect almost any frequency response and do so over an interval determined by the length of the delay line which forms the backbone of the filter. In the delay line successive samples of a received signal are subject to the application of fixed or variable weighting coefficients the aggregate of which determines the value of each successive sample output by the filter. The longer the delay line, i.e. the greater the number of taps, the higher the order of the filter and the more finely tuned the response of the filter. After all taps in the delay line are evaluated the delay line is incremented by one sample and the process is repeated to determine the value of the next sample.
A subset of FIR filters identified as time domain equalizers handle the demanding task of equalizing in the time domain the varying propagation delays associated with high speed multipath wired and wireless communications associated with Digital TV broadcast and Cellular telecommunications for example. In these applications it is not unusual for the number of taps in the filter to number several hundred. All the processing associated with aggregating filter values from all the taps must take place at rates consistent with the broadcast or communication channel, which can extend to many Gigabits per second.
What is needed is an improved FIR design.